Tortilla Curtain by T.C. Boyle

Delaney Mossbacher is a wealthy, conscientious liberal on his way to the recycling center when he hits a pedestrian with his car as he's driving in the suburbs of Los Angeles. The man hit is Candido Rincon, a poor, illegal immigrant from Mexico. Feeling guilty, Delaney gives Candido twenty dollars to compensate for his injuries, and the two men go their separate ways. Yet with the accident, Delaney and Candido's lives become woven together for the rest of the novel.